1. Field of the Invention
The present invention relates to an image processing system in an image processing apparatus, capable of efficiently logically filtering run-length coded binary image data.
2. Description of the Related Art
In an image processing apparatus such as an OCR (Optical Character Reader) and an optical drawing reader, to-be-processed image data is generally expressed as a binary image using two types of data, i.e., 0 and 1. When a binary image thus expressed is subjected to a logic filtering process such as feature detection and thinning (processing to convert a thick line segment to a thin line segment), it is usually subjected to TV raster scanning to extract a pattern of N.times.M pixels having an interest pixel as a center, and is then subjected to predetermined processing in accordance with the extracted pattern. However, in order to execute such processing for extracting the N.times.M pattern, a memory storing the binary image must be accessed frequently. Since the number of access times is large, the processing speed becomes low.
When the to-be-processed image data is to be expressed as binary data in units of pixels, the data amount of the image data becomes very large. For this reason, the image data is subjected to run-length coding in units of rows, so that the image data is expressed in a compressed data form. When run-length coded to-be-processed image data is subjected to the above-mentioned logic filtering process, however, the compressed image data must be expanded to the original image data expressed in units of pixels. When the original image data is subjected to predetermined logic filtering processing, it must be then subjected to run-length coding again. In this manner, when run length coded to-be-processed image data is subjected to the logic filtering processing, the entire image processing becomes very complicated.
Conventionally, as described above, when binary image data is subjected to the logic filtering processing, the memory storing the binary image data must be accessed frequently in order to obtain the N.times.M pixel pattern as the unit pattern of the image data to be processed, resulting in a low processing speed. In addition, when the to-be-processed image data is given in the form of run-length coded data, the run-length coded data must be restored to the original binary image data, resulting in logic filtering of a very low processing efficiency.